On September 15, 2000, about 2045 Eastern Daylight Time, a Boeing 737-49R, N461PR, operated by Pro Air Inc., as flight 325, was substantially damaged during pushback for taxi at the La Guardia Airport (LGA), Flushing, New York. The 2 flight crewmembers, 3 flight attendants, and 53 passengers were not injured. Visual meteorological conditions prevailed and an instrument flight rules flight plan had been filed for the flight destined for the Detroit City Airport, Detroit, Michigan. The scheduled passenger flight was conducted under 14 CFR Part 121. According to a Federal Aviation Administration (FAA) inspector, the airplane was being pushed back from gate C-4, by three Signature Flight Support ground crew employees. During the pushback, the airplane's rudder struck an MD-80, which was parked at a gate across from N461PR. According to a Signature Flight Support representative, both "wing walkers" were equipped with night wands, and had signaled the tug driver to stop prior to the accident. One wing walker stated he noticed that the airplane was getting "very close" to the MD-80, and signaled the tug operator to stop "several times" before the accident. The tug operator stated, "...one of the wing walkers signaled me to stop, but I was looking at the other wing walker. He told me to stop, but when I hit the brake it was too late...." According to a Signature Flight Support manager, the tug operator had been hired and began performing airplane pushbacks in December 1998. The weather reported at LGA, at 2051, included: a visibility of 10 statue miles, and scattered clouds at 8, 500 feet msl.